upgrading HDD in My Book World Edition (white light) single HDD

i have WD My Book World Edition Firmware 01.02.06 with MioNet 4.3.1.13 built on Thu Oct 21 10:19:41 CST 2010

it contains with WD 1TB WD10EADS.

lately the hard drive becomes full and i want to upgrade to 2TB WD20EARX.

the problem is WD20EARX is SATA3, is it possible to upgrade to SATA3 even if there is just only SATA2 performance. since WD20EARS (SATA2) and WD20EARX (SATA3) price is already same, i'm just anticipating for future.